Fuel dripping from EVAP cannister - end of my rope

spstan

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I bought a brand new Holley 4175 carb for my 1975 Chrysler. Car started and ran good for about two years. Leak developed (I think it was accelerator pump). Rebuilt carb (carefully) over winter. Car ran good for about 4 weeks. Came out of library, car flooded and had fuel spouting out of the carb throat and dripping from bottom of EVAP cannister. Cleaned the plugs and lowered the floats, got the car started and barely made it back home. Car would not hold idle.

Talked to my drag race car driver neighbor and he said to drain the EVAP cannister, replace the needles, seats and floats. Hard for me to believe that floats would go bad after only 2 years.

Question is what is causing fuel to drain from the front bowl into the EVAP cannister. The connecting hose that runs from the top of the bowl to the cannister comes off the front bowl at a position that is much higher than the top of the float. Why would so much gas drain into the EVAP cannister? Paul
 
Stuck needle and seat or bad float would do that.
Big; how do you check for a bad float? I saw something about sticking it in boiling water and looking for air bubbles coming out of it. I've never tried this. Paul
 
Big; how do you check for a bad float? I saw something about sticking it in boiling water and looking for air bubbles coming out of it. I've never tried this. Paul
I never heard about sticking it in in boiling water. I suppose water would work.

If you shake the float, you might hear gas bouncing around in it.
 
The bottom of the vac cannister should be open with a fiberglass "filter" there. That is also the vent for the fual tank. The charcoal absoerbs the vapors and hold them until the vac bias is such that they can be re-cycled into the engine for burning.

The ONE problem with many Holley carbs is that the accel pump diaphram is on the bottom of the float bowl. When ethanol degrades it, it can leak the fuel from the float bowl onto the intake manifold. IF that was all that was the matter, Holley sells pump diaphrams separately. No need for a kit to get one.

Where the canister line attaches to the carb is basically where the old bowl vent would be. IF fuel gets that high in the bowl, it'll probably be forced into the carb venturis, too.

As the canister is an evaporative emissions item, you can unhook the line from it to the carb with no operational issues . . . other than the possible fuel over-supply to the carb from it. You can plug the line from the canister and see what happens, then. If fuel still leaks from the canister, then you know the fuel is coming directly from the gas tank. In this troubleshooting, you can also remove and plug the vac line(s) from the carb to the canister, too. Separating the canister completely from the engine and carb in the process. Hopefully such separation might help narrow things down a bit.

Personally, I would NOT use heat to check for a leak of a metal float! You CAN let the float sit in water overnight and then check to see if any seeped into the float via a poor solder. PLUS, unless you go buy a "burner/throwaway" inexpensive metal pot to put the water into for the float, your spouse might have some thoughts on that!

How NEW is the gas cap? I believe it's supposed to have some "pressure relief" function in it. How full was the fuel tank when all of this happened and at what ambient temperature?

Just some thoughts,
CBODY67
 
check your fuel pressure. i had a pump go bad once and it was putting out over 12 psi.
 
parts can go bad anytime.
a day without a bad part is good day. doesn't happen often.
how do you check for a bad float?
it's a float. put it in water and it should........float. brass float correct? dry it off and put it over an incandescent light bulb. if there's fuel in it the heat of the bulb will cause it to boil out of any pin hole. be careful with gas and light bulbs though. gas on a bulb can cause the bulb to shatter and ignite the gas.
 
As always bored people posting the absurd.
The needle n seat/float assy is sticking and/or miss-adjusted allowing the carb to overfill. why it is doing that is unknown as i do not have carb in front of me.
Your drag racing neighbor is the last person i would ask for help.
PERIOD
 
...why it is doing that is unknown as i do not have carb in front of me.
One of these days soon I will get off my arse and get that Chrysler carb in front of me (again) and maybe do some old school driving again this summer. Maybe.
 
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